Drive device for fuel injection device

ABSTRACT

The objective of the present invention is to correct deviation in the injection amount and changes in the injection timing when the voltage of a high-voltage source for a drive device decreases. This drive device for a fuel injection device is equipped with a function whereby, when the pulse width of the injection pulse is set to an energization time 815 that closes a valve after a drive current has been switched to a maintenance current, the injection pulse width when the voltage of a high-voltage source has decreased is corrected so as to be longer than the injection pulse width when the voltage of the high-voltage source has not decreased, and, when the pulse width of the injection pulse is set to an energization time 804′ that closes the valve before the drive current has been switched to the maintenance current, the absolute value of the amount of correction of the injection pulse width is made smaller than when the injection pulse width is set to the energization time 815 that closes the valve after the drive current has been switched to the maintenance current.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/527,060, filed May 16, 2017, which is a National Stage Application ofPCT/JP2015/076600, filed Sep. 18, 2015, which claims the benefit of andpriority to Japanese Patent Application No. 2014-234009, filed Nov. 19,2014, the entire contents of each of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a drive device for driving a fuelinjection device of an internal combustion engine.

BACKGROUND ART

In recent years, with the strengthening of exhaust regulation, inengines, suppression of the total amount of unburnt particles (PM:Particulate Matter) during mode running and suppression of the number ofunburned particles (PN: Particulate Number) which is the number thereofare required, so that a fuel injection device capable of controlling aminute injection amount is required. As a means for suppressing thegeneration of unburned particles, it is effective to inject the fuelspray during one combustion stroke dividedly into a plurality of times(hereinafter referred to as split injection). By performing splitinjection, adhesion of fuel to a piston and cylinder wall surface can besuppressed, so the injected fuel is liable to be vaporized; accordingly,it is possible to suppress the total amount (PN) of unburned particlesand the number of unburned particles, which is the number thereof. In anengine that performs split injection, it is necessary to injectdividedly into a plurality of times the fuel that has been injected atone time; therefore, in the fuel injection device, it is necessary tocontrol a minute injection amount as compared with the conventional fuelinjection device. Further, in multistage injection, it is easy to obtainthe effect of suppressing the number of unburned particles by increasingthe number of injections; therefore, improvement of responsiveness ofthe fuel injection device and reduction of interval of fuel injectionduring the combustion stroke are required.

Generally, the injection amount of the fuel injection device iscontrolled by a pulse width of an injection pulse output from an enginecontrol unit (ECU). A normally closed electromagnetic fuel injectionvalve (electromagnetic fuel injection device) has biasing means forgenerating a force in a valve closing direction. A drive portionincludes a coil, a core and a mover. By supplying a current to the coil,a suction force is generated between the core and the mover. When thesuction force exceeds the force in the valve closing direction, a valvebody separates from the valve seat and a valve opening starts.Subsequently, by stopping the current supply to the coil, a valveclosing starts when the suction force generated between the core and themover decreases and becomes smaller than the force in the valve closingdirection. Generally, in order to quickly shift from the closed valvestate to the valve open state, a drive circuit of the electromagneticfuel injection device first applies a high voltage from a high voltagesource to the coil when the injection pulse is output, and then performscontrol to rapidly raise the current of the coil. Thereafter, after themover moves away from the valve seat and moves in the direction towardthe core, switching control is performed so that a constant current issupplied to the coil by switching the application of the voltage to alow voltage. In many cases, the high voltage source stores the voltageof a low voltage source; however, in the case of performing re-injectionof fuel under a condition that the injection interval of a multistageinjection becomes small and the voltage value of the high voltage sourcedoes not return to the initial value, a current value flowing throughthe coil varies depending on a difference in the voltage applied to thecoil, and the injection amount variation may occur even under acondition of supplying the same injection pulse width.

As a means for suppressing variation in the injection amount asdescribed above, there is a method disclosed in Patent Literature 1.Patent Literature 1 discloses a control method that estimates a voltageapplied to a coil and lengthens a command injection period according toa decrease amount when the estimated value is lower than a specifiedvalue.

Further, for example, Patent Literature 2, discloses a control device ofa fuel injection device that measure a time Tp from the start ofenergization until a current reaches a peak current value, and delaysthe energization stop by a delay time than the falling time of aninjection command signal, as the amount of time Tp is longer than thereference value.

PRIOR ART DOCUMENT Patent Literature

PTL 1: JP 2005-171928 A

PTL 2: JP 2011-52631 A

SUMMARY OF THE INVENTION Technical Problem

In the fuel injection device, by supplying and stopping a drive currentto a solenoid (coil), a magnetic attraction force is generated and/orextinguished in the mover to open and/or close the valve body. Under acondition of multistage injection, the time from the stop of fuelinjection of the other cylinder to the next fuel injection is shortenedso that the voltage of a high voltage source of a drive device does notreturn to an initial value; accordingly, it is necessary to inject fuelunder a condition that the applied voltage to the coil is small.However, under a condition that high voltage decreases, the currentflowing through the coil decreases and the magnetic attraction forceacting on the mover decreases, so that the time until the valve bodyopens becomes long, and the injection amount injected before the valveopens decreases. Under a condition that the injection pulse is stoppedwhen after reaching the switching control period such that the injectionpulse is large or the voltage applied to the coil is switched to the lowvoltage and constant current is supplied, in the case where the voltageof the high voltage source is lower than when the voltage does notdecrease, the injection amount decreases as the time until the valvebody opens becomes longer.

On the other hand, in multistage injection, it is important to reducevariation in the injection amount in a range where the controllableinjection amount is small. In this range, the change in the injectionamount in the case where the voltage of the high voltage source drops issmaller than in the range where the injection pulse is large, or theinjection amount may become larger in the case where the voltagedecreases. Therefore, in order to suppress variation in the injectionamount caused by the voltage of the high voltage source decreasing in aregion where the controllable injection amount is small and in theregion where the injection pulse width is large, it has been necessaryto change the correction method of the injection pulse depending on therange of the injection pulse and the value of the drive current.

An object of the present invention is to correct variation in theinjection amount and injection timing in the case where the voltage ofthe high voltage source of the drive device decreases.

Solution to Problem

In order to solve the above problem, the present invention provides adrive device for a fuel injection device, the drive device beingconfigured to open a valve body of an electromagnetic fuel injectiondevice by energizing a solenoid to apply a magnetic attraction forcebetween a fixed core and a mover, the drive device including a functionof applying a high voltage to the solenoid when the valve body opens,and after the drive current flowing through the solenoid reaches apredetermined current value, switching the drive current to a holdingcurrent smaller than the predetermined current value to maintain a valveopen state, the drive device for the fuel injection device beingconfigured to generate an injection pulse and control a time forenergizing the solenoid with a pulse width of the injection pulse, thedrive device including a function of, when the pulse width of theinjection pulse is set to an energization time at which the valve bodyis closed after the drive current is switched to the holding current,correcting the pulse width of the injection pulse in the case where thefuel injection timing or the fuel injection period overlaps between thecylinders so as to be longer than the pulse width of the injection pulsein the case where the fuel injection timing or the fuel injection perioddoes not overlap, and when the pulse width of the injection pulse is setto an energization time at which the valve body is closed before thedrive current is switched to the holding current, in comparison with thecase where the pulse width of the injection pulse is set to theenergization time at which the valve body is closed after the drivecurrent is switched to the holding current, reducing an absolute valueof the correction amount of the pulse width of the injection pulse.

Advantageous Effects of Invention

According to the present invention, when the voltage of the high voltagesource generating the high voltage decreases, the correction amount ofthe injection amount can be appropriately determined according to therange of the injection pulse width; therefore, it is possible tosuppress variation in the injection amount due to voltage drop of thehigh voltage source. In addition, by correcting the injection pulsewidth so as to be smaller than the range where the injection pulse widthis large in the range where the injection pulse width is small, it ispossible to provide a drive device capable of reducing the controllableminimum injection amount.

The problems, configurations, and effects other than those describedabove will be clarified from the description of the embodiments below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of a fuelinjection system in a case where a fuel injection device, a pressuresensor, a drive device, and an engine control unit (ECU) according to afirst embodiment of the present invention are mounted in an in-cylinderdirect injection type engine.

FIG. 2 is a longitudinal sectional view of the fuel injection deviceaccording to the first embodiment of the present invention and anexample of a configuration of a drive circuit and an ECU for driving thefuel injection device.

FIG. 3 is an enlarged cross-sectional view showing a cross section of adrive portion of the fuel injection device according to the firstembodiment of the present invention in an enlarged manner.

FIG. 4 is a view showing a relationship between time and a generalinjection pulse, a driving voltage, a drive current that drive the fuelinjection device, and a displacement amount of a valve body and a mover.

FIG. 5 is a view showing details of a drive device for the fuelinjection device according to the first embodiment of the presentinvention.

FIG. 6 is a view showing a relationship of a fuel injection timing ofeach cylinder in a case where multistage fuel injection is performedthree times in an intake stroke and twice in a compression stroke duringone combustion cycle including the intake stroke, the compressionstroke, an expansion stroke, and an exhaust stroke, for the drive devicefor the fuel injection device according to the first embodiment.

FIG. 7 is a view showing a relationship between time and a voltage valueof a high voltage source, an injection pulse, a drive current, and avalve body displacement amount body in the period of 604 in FIG. 6, fora first cylinder and a third cylinder.

FIG. 8 is a view showing a relationship between an injection pulse widthand a fuel injection amount and a relationship between an injectionpulse width and an injection amount deviation in a case where thevoltage value of the high voltage source does not decrease (Q₈₀₁) andthe case where the voltage value decreases (Q₈₀₂).

FIG. 9 is a view showing a relationship between time and a voltage valueof a high voltage source, an injection pulse, a drive current, and avalve body displacement amount under a condition that the injectionpulse is small (a condition that an injection pulse width Ti is 804 inFIG. 8).

FIG. 10 is a view showing a relationship between time and a voltage of ahigh voltage source, an injection pulse, a drive current, a magneticattraction force acting on a mover, and a valve body displacement amountunder a condition that the voltage value of the high voltage source doesnot decrease and a condition that the voltage decreases.

FIG. 11 is a view showing a relationship between a boosted voltage andfuel injection timing under three conditions in which fuel pressuresupplied to a fuel injection device is different, for the drive devicefor the fuel injection device according to the first embodiment.

FIG. 12 is a view showing, in a case where a voltage value of a highvoltage source does not decrease and a case where the voltage valuedecreases, a drive current and a valve body displacement amount at aninjection pulse width at a point 815 in FIG. 8, and a drive current anda valve body displacement amount at an injection pulse width at a point802, for a drive device for a fuel injection device according to asecond embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below withreference to the drawings.

First Embodiment

Hereinafter, a fuel injection system including a fuel injection device,a pressure sensor, and a drive device according to the present inventionwill be described with reference to FIGS. 1 to 7.

First, the configuration of the fuel injection system will be describedwith reference to FIG. 1. FIG. 1 is a schematic diagram showing aconfiguration of a fuel injection system in a case where a fuelinjection device, a pressure sensor, a drive device, and an enginecontrol unit (ECU) according to a first embodiment of the presentinvention are mounted in an in-cylinder direct injection type engine.The configuration of FIG. 1 is also applied to a second embodiment.

The fuel injection system of the present embodiment includes fuelinjection devices 101A to 101D, a fuel rail 105, a pressure sensor 102,a fuel pump 106, a fuel pipe 120, a drive device 150, an ECU, and thelike.

The fuel injection devices 101A to 101D are installed in each cylinderso that fuel spray from an injection hole is directly injected intocombustion chambers 107A to 107D. The fuel is boosted by the fuel pump106, sent to the fuel rail 105, and delivered to the fuel injectiondevices 101A to 101D. Fuel pressure varies due to the flow rate of thefuel discharged by the fuel pump 106, and the balance of the injectionamount of the fuel injected into the respective combustion chambers 107Ato 107D by the fuel injection devices 101A to 101D provided in eachcylinder of the engine; however, the fuel pressure is controlled suchthat a discharge amount from the fuel pump 106 is controlled with apredetermined pressure as a target value based on information from thepressure sensor 102 provided on the fuel rail 105. The number ofcylinders and the number of the fuel injection devices 101A to 101D arenot limited to the number of the present embodiment.

The fuel injection from the fuel injection devices 101A to 101D iscontrolled by the injection pulse width sent from the ECU 104, thisinjection pulse is input to the drive circuit 103 of the fuel injectiondevices 101A to 101D, and the drive circuit 103 determines a drivecurrent waveform based on a command from the ECU 104 and supplies thedrive current waveform to the fuel injectors 101A to 101D for a timebased on the injection pulse. Note that the drive circuit 103 may bemounted as a component integrated with the ECU 104 or a board. The drivecircuit 103 and the ECU 104 are collectively referred to as a drivedevice 150.

The drive circuit 103 is provided in each of the fuel injection devices101A to 101D. As will be described later, a boosting circuit 514 (seeFIG. 5) in the drive circuit 103 may be shared by a plurality of fuelinjection devices. The drive circuit 103 provided for each of the fuelinjection devices 101A to 101D may be provided dispersedly on aplurality of substrates, or may be provided together on one substrate.Alternatively, the drive circuit 103 dispersedly provided on a pluralityof substrates may be housed in one case. Hereinafter, the drive circuit103 of each fuel injection device 101A to 101D will be described withoutdistinction.

Next, with reference to FIG. 2, a configuration and basic operation ofthe fuel injection devices 101A to 101D and the drive device 150 thereofwill be described. FIG. 2 is a longitudinal sectional view of the fuelinjection devices 101A to 101D according to the present embodiment andan example of a configuration of the drive circuit 103 and the ECU 104for driving the fuel injection devices 101A to 101D. In FIG. 2, the samesymbols are used for components equivalent to those in FIG. 1.

The ECU 104 takes in a signal indicating the state of the engine fromvarious sensors, and calculates the width of the injection pulse and theinjection timing for controlling the injection amount of the fuelinjected from the fuel injection devices 101A to 101D in accordance withthe operating condition of the internal combustion engine. In addition,the ECU 104 is provided with an A/D converter and an I/O port for takingin signals from various sensors. The injection pulse output from the ECU104 is input to the drive circuit 103 of the fuel injection devices 101Ato 101D via the signal line 110. The drive circuit 103 controls thevoltage to be applied to the solenoid 205 and supplies a current to thesolenoid 205. The ECU 104 communicates with the drive circuit 103through a communication line 111, can change the drive current generatedby the drive circuit 103 according to the pressure of the fuel suppliedto the fuel injection devices 101A to 101D and an operating conditionand can change the set values of the current and time.

Next, a configuration and operation of the fuel injection devices 101Ato 101D will be described with reference to FIGS. 2 and 3. FIG. 3 is anenlarged cross-sectional view showing a cross section of a drive portionof the fuel injection devices 101A to 101D according to the firstembodiment of the present invention in an enlarged manner. In FIG. 3,the same symbols are used for components equivalent to those in FIG. 2.

The fuel injection devices 101A to 101D shown in FIGS. 2 and 3 arenormally closed electromagnetic valves (electromagnetic fuel injectiondevice), and when the solenoid 205 is not energized, a valve body 214 isurged in a valve closing direction by a spring 210 which is a firstspring, and the valve body 214 is in close contact with a valve seat 218and is in the closed state. In the valve closed state, an urging forceby a second spring (return spring) 212 acting in the valve openingdirection acts on a mover (movable core) 202. At this time, since theforce of the spring 210 acting on the valve body 214 is larger than theforce of the return spring 212, an end face 302 of the mover 202contacts the valve body 214, and the mover 202 is stationary. Inaddition, the valve body 214 and the mover 202 are configured to bedisplaceable relative to each other, and are enclosed in a nozzle holder201. Furthermore, the nozzle holder 201 has an end face 303 which is aspring seat of the return spring 212. The force due to the spring 210 isadjusted at the time of assembly by the pushing amount of a springretainer 224 fixed to the inner diameter of a fixed core 207.

The fixed core 207, the mover 202, the nozzle holder 201, and thehousing 203 constitute a magnetic circuit, and the fuel injectiondevices 101A to 101D have a gap between the mover 202 and the fixed core207. A magnetic throttling part 211 is formed in a portion correspondingto a gap between the mover 202 of the nozzle holder 201 and the fixedcore 207. The solenoid 205 is attached to the outer peripheral side ofthe nozzle holder 201 in a state of being wound around a bobbin 204. Arod guide 215 is provided so as to be fixed to the nozzle holder 201 inthe vicinity of a tip portion of the valve body 214 on the side of thevalve seat 218. The valve body 214 is guided by the movement in thevalve axial direction by the two sliding parts of the inner peripheralsurface of the fixed core 207 of the valve body 214 and the rod guide215. An orifice cup 216 having the valve seat 218 and a fuel injectionhole 219 is fixed to a tip portion of the nozzle holder 201, and sealsan internal space (fuel passage) provided between the mover 202 and thevalve body 214 from the outside.

The fuel is supplied from the fuel rail 105 provided upstream of thefuel injectors 101A to 101D to the fuel injection devices 101A to 101D.The fuel supplied to the fuel injection devices 101A to 101D flows to atip of the valve body 214 through a first fuel passage hole 231. Whilethe valve body 214 maintains the closed state, the fuel is sealed by theseat portion formed at the end portion of the valve body 214 facing thevalve seat 218 and the valve seat 218. When the valve body opens, adifferential pressure is generated between the upper portion and thelower portion of the valve body 214 by the fuel pressure. Thisdifferential pressure is obtained by multiplying the fuel pressure and apressure receiving area of a contact diameter (hereinafter referred toas a seat diameter) between the valve body 214 and the valve seat 218.Due to the differential pressure and the load of the spring 210, thevalve body 114 is pushed in the valve closing direction. When a currentis supplied from the drive circuit 103 to the solenoid 205 through awiring member 209 in the valve closed state, a magnetic field isgenerated in the magnetic circuit. Then, a magnetic flux passes betweenthe fixed core 207 and the mover 202, and a magnetic attraction forceacts on the mover 202. At a timing when the magnetic attraction forceacting on the mover 202 exceeds the differential pressure and the loadby the set spring 210, the mover 202 starts displacement (valve openingoperation) toward the fixed core 207. At this time, the end face 302 ofthe mover 202 abuts against a position regulating portion (flangeportion) 303 of the valve body 214, and the mover 202 and the valve body214 are integrally displaced.

After the valve body 214 starts the valve opening operation, the mover202 moves to the position of the fixed core 207, and the mover 202collides with the fixed core 207. After the mover 202 collides with thefixed core 207, the mover 202 performs an action of receiving a reactionforce from the fixed core 207 and bouncing back; however, the mover 202is attracted to the fixed core 207 by the magnetic attraction forceacting on the mover 202, and then stops. At this time, since a forceacts on the mover 202 in the direction of the fixed core 207 by thereturn spring 212, it is possible to shorten the time until convergenceof the rebound. Small rebounding action shortens the time during which agap between the mover 202 and the fixed core 207 becomes large;therefore, stable operation can be performed even for a smallerinjection pulse width. During the rebounding action of the mover 202,the mover 202 is displaced away from the position regulating portion 303of the valve body 214.

The mover 202 and the valve body 214 which have completed the valveopening operation in this manner are stationary in the valve open state.In the valve open state, a gap is formed between the valve body 202 andthe valve seat 218, and fuel is injected from the injection hole 219.The fuel passes through a center hole 207 a provided in the fixed core207 and a lower fuel passage hole 305 provided in the mover 202 andflows in the downstream direction. In this valve open state, the endface 302 of the mover 202 is in contact with the position regulatingportion (flange portion) 303 of the valve body 214.

When the energization to the solenoid 205 is interrupted, the magneticflux that has been generated in the magnetic circuit disappears and themagnetic attraction force also disappears. As the magnetic attractionforce acting on the mover 202 disappears, so that the mover 202 and thevalve body 214 are pushed back to a valve closing position where themover 202 and the valve body 214 contact the valve seat 218 by the loadof the spring 210 and the differential pressure. In this valve closingoperation, the end face 302 of the mover 202 abuts against the positionregulating portion (flange portion) 303 of the valve body 214, and themover 202 and the valve body 214 are integrally displaced.

Furthermore, when the valve body 214 is closed from the valve openstate, after the valve body 214 comes into contact with the valve seat218, the mover 202 separates from the position regulating portion(flange portion) 303 of the valve body 214 and continues displacement inthe valve closing direction. After the displacement of the mover 202 inthe valve closing direction is continued for a certain period of time,the mover 202 is returned to the initial position of the closed valvestate by the return spring 212. At the moment when the valve body 214 isclosed, by separating the mover 202 from the valve body 214, the mass ofthe movable member at the moment when the valve body 214 collides withthe valve seat 218 can be reduced by the mass of the mover 202.Therefore, the collision energy when the valve body 214 collides withthe valve seat 218 can be reduced, thereby suppressing the bound of thevalve body 214 caused by the collision of the valve body 214 against thevalve seat 218.

In the fuel injection devices 101A to 101D of the present embodiment,the valve body 214 and the mover 202 generate a relative displacementfor a short period of time at the moment when the mover 202 collideswith the fixed core 207 at the time of valve opening and at the momentwhen the valve body 214 collides with the valve seat 218 at the time ofvalve closing, so that it is possible to suppress the bound of the mover202 with respect to the fixed core 207 and the bound of the valve body214 with respect to the valve seat 218.

Next, the injection pulse output from the ECU 104, the drive voltage atboth ends of the terminal of the solenoid 205 of the fuel injectiondevices 101A to 101D, the drive current (excitation current), thedisplacement amount of the valve body 214 and the mover 202 (valve bodybehavior) will be described with reference to FIGS. 4 and 5. FIG. 4 is aview showing a relationship between time and a general injection pulse,a driving voltage, a drive current that drive the fuel injection device,a displacement amount of a valve body, and a displacement of a mover.FIG. 5 is a view showing details of a drive device for the fuelinjection device according to the first embodiment of the presentinvention.

When an injection pulse is input to the drive circuit 103, the drivecircuit 103 energizes switching elements 505, 506 to apply a highvoltage 401 from a high voltage source boosted to a voltage higher thanthe battery voltage to the solenoid 205, and starts to supply a currentto a solenoid 205. When the current value reaches a peak current valueI_(peak) preset in the ECU 104, the application of the high voltage 401is stopped. Thereafter, when the switching element 505 and the switchingelement 506 are de-energized, by a counter electromotive force due tothe inductance of a fuel injection device 540, a diode 509 and a diode510 are energized, the current is fed back to a voltage source VH side,and the current supplied to the fuel injection device 540 rapidlydecreases from the peak current value I_(peak) as a current 402. Whenthe switching element 506 is turned ON during the transition period fromthe peak current value I_(peak) to a current 403, a current due to acounter electromotive force energy flows to a ground potential 515 side.A current regenerates in the circuit, a voltage of approximately 0 V isapplied to the solenoid 205, and the current gently decreases. When thecurrent value becomes smaller than a predetermined current value 404,the drive circuit 103 supplies a current to the switching element 506,applies a battery voltage VB by energizing and de-energizing a switchingelement 507, and provides a switching period for performing control sothat the predetermined current 403 is maintained. When a fuel pressuresupplied to the fuel injection device 540 increases, a fluid forceacting on the valve body 214 increases, and the time until the valvebody 214 reaches a target opening degree increases. As a result, anarrival timing to the target opening degree may be delayed with respectto an arrival time of the peak current I_(peak); however, when thecurrent is rapidly reduced similar to the current 402, the magneticattraction force acting on the mover 202 rapidly decreases, so that thebehavior of the valve body 214 becomes unstable. In some cases, thevalve closing may be started regardless of energization. In the casewhere the current is gradually decreased by turning ON the switchingelement 506 during transition of the current 403 from the peak currentI_(peak), it is possible to suppress the decrease in the magneticattraction force, ensure the stability of the valve body 214 at the highfuel pressure, and suppress the variation in the injection amount.

The fuel injection device 540 (101 A to 101 D) is driven by such asupply current profile. During the period from the application of thehigh voltage 401 to the peak current value I_(peak), the mover 202 andthe valve body 214 start to displace at timing t₄₁. Thereafter, themover 202 and the valve body 214 reach the maximum opening degree. Atthe timing when the mover 202 reaches the maximum opening degree, themover 202 collides with the fixed core 207, and the mover 202 performs abound operation with the fixed core 207. Since the valve body 214 isconfigured to be displaceable relative to the mover 202, the valve body214 moves away from the mover 202, and the displacement of the valvebody 214 overshoots beyond the maximum opening degree. Thereafter, dueto the magnetic attraction force generated by the holding current 403and the force in the valve opening direction of the return spring 212,the mover 202 is stationary at a position of a predetermined maximumopening degree. In addition, the valve body 214 is seated on the mover202 and is stationary at the position of the maximum opening degree, andis in the valve opening state.

In the case of a fuel injection device having a movable valve in whichthe valve body 214 and the mover 202 are integrated, the displacementamount of the valve body 214 does not become larger than the maximumopening degree. The amount of displacement of the mover 202 and thevalve body 214 after reaching the maximum opening is equal.

Furthermore, with reference to FIG. 5, the configuration of the drivedevice for the fuel injection device according to the first embodimentof the present invention will be described in detail.

A CPU 501 is incorporated in the ECU 104, for example. The CPU 501 takesin a signal indicating the state of the engine of a pressure sensor 102attached to the fuel rail 105, an A/F sensor for measuring the amount ofair flowing into an engine cylinder, an oxygen sensor for detecting anoxygen concentration of an exhaust gas discharged from the enginecylinder, a crank angle sensor, and the like, and calculates a width Ti(that is, the injection amount) of the injection pulse and the injectiontiming for controlling the injection amount injected from the fuelinjection device 540 (101A to 101D) according to the operating conditionof the internal combustion engine. The CPU 501 outputs the injectionpulse width Ti to a driving IC 502 of the fuel injection device throughthe communication line 504. Thereafter, the driving IC 502 is switchedthe energization and de-energization of the switching elements 505, 506,and 507 and supplies the drive current to the fuel injection device 540.

The switching element 505 is connected between a high voltage sourcehigher than a voltage source VB input to the drive circuit and a highvoltage side terminal of the fuel injection device 540. The switchingelements 505, 506, and 507 are configured by, for example, FETs,transistors, or the like, and can switch between energization andde-energization of the fuel injection device 540. A boosted voltage VHwhich is an initial voltage value of the high voltage source is, forexample, 60 V, and is generated by boosting the battery voltage by theboosting circuit 514. The boosting circuit 514 includes, for example, amethod using a DC/DC converter or the like, and a method using a coil530, a transistor 531, a diode 532, and a capacitor 533. In the casewhere the boosting circuit 514 is configured by the latter method, whenthe transistor 531 is turned ON, the battery voltage VB flows to aground potential 534 side; however, when the transistor 531 is turnedOFF, a high voltage generated in the coil 530 is rectified through thediode 532, and electric charge is accumulated in the capacitor 533. Thistransistor is repeatedly turned ON and OFF until the boosted voltage VHis reached, and the voltage of the capacitor 533 is increased. Thetransistor 531 is connected to the IC 502 or the CPU 501, and theboosted voltage VH output from the boosting circuit 514 is detected bythe IC 502 or the CPU 501. In the present embodiment, the boostedvoltage VH is input to the IC 502 by a wiring 551, and the boostedvoltage VH is detected by the IC 502.

Besides, between a power source side terminal 590 of the solenoid 205and the switching element 505, a diode 535 is provided so that a currentflows from the boosting circuit 514 which is a second voltage sourcetoward the solenoid 205 and the contact potential 515. Besides, betweena power source side terminal 590 of the solenoid 205 and the switchingelement 507, a diode 511 is provided so that a current flows from abattery voltage source VB toward the solenoid 205 and the contactpotential 515. Since the diode 535 and the diode 511 are provided, whilethe switching element 506 is energized, a current does not flow from theground potential 515 toward the solenoid 205, the battery voltage sourceVB, and the second voltage source 514. In addition, in the ECU 104, aregister and a memory are mounted in order to store numerical datanecessary for engine control such as calculation of injection pulsewidth. The register and the memory are included in the drive device 150or the CPU 501 in the drive device 150.

Furthermore, the switching element 507 is connected between the lowvoltage source and the high voltage terminal of the fuel injectiondevice. The low voltage source VB is, for example, a battery voltage,and its voltage value is about 12 to 14 V. The switching element 506 isconnected between the low voltage side terminal of the fuel injectiondevice 540 and the ground potential 515. The driving IC 502 detects thecurrent value flowing through the fuel injection device 540 by means ofthe current detection resistors 508, 512, and 513. On the basis of thedetected current value, energization and de-energization of theswitching elements 505, 506, 507 is switched to generate a desired drivecurrent. Diodes 509 and 510 are provided to apply a reverse voltage tosolenoid 205 of the fuel injection device and to rapidly reduce thecurrent being supplied to solenoid 205. The CPU 501 communicates withthe driving IC 502 through a communication line 503. On the basis of thepressure of the fuel supplied to the fuel injection device 540 andoperating conditions, it is possible to switch the drive currentgenerated by the driving IC 502. Both ends of the resistors 508, 512,and 513 are connected to the A/D conversion port of the IC 502 bywirings 550, 551, 580, 581, 552, and 553, and are configured so that thevoltage applied across the resistors 508, 512, and 513 can be detectedby the IC 502.

Next, with reference to FIGS. 6, 7, 8 and 9, a method of correcting theinjection amount in the first embodiment will be described. FIG. 6 is aview showing a relationship of a fuel injection timing of each cylinderin a case where multistage fuel injection is performed three times in anintake stroke and twice in a compression stroke during one combustioncycle including the intake stroke, the compression stroke, an expansionstroke, and an exhaust stroke, for the drive device for the fuelinjection device according to the first embodiment. FIG. 7 is a viewshowing a relationship between time and a voltage value of a highvoltage source, an injection pulse, a drive current, and a valve bodydisplacement amount in the period of 604 in FIG. 6, for a first cylinderand a third cylinder. FIG. 8 is a view showing a relationship between aninjection pulse width and a fuel injection amount and a relationshipbetween an injection pulse width and an injection amount deviation in acase where the voltage value of the high voltage source does notdecrease (Q₈₀₁) and the case where the voltage value of the high voltagesource decreases (Q₈₀₂). FIG. 9 is a view showing a relationship betweentime and a voltage value of a high voltage source, an injection pulse, adrive current, and a valve body displacement amount under a conditionthat the injection pulse is small (a condition that an injection pulsewidth Ti is 804 in FIG. 8). FIG. 10 is a view showing a relationshipbetween time and a voltage of a high voltage source, an injection pulse,a drive current, a magnetic attraction force acting on a mover 202, anda valve body displacement amount under a condition that the voltagevalue of the high voltage source does not decrease and a condition thatthe voltage decreases. FIG. 11 is a view showing a relationship betweena boosted voltage and fuel injection timing under three conditions inwhich fuel pressure supplied to a fuel injection device is different,for the drive device for the fuel injection device according to thefirst embodiment.

A method of correcting the injection amount will be described withreference to FIGS. 6, 7, and 8. First, a condition under which theinjection timing overlaps among the cylinders will be described. In adirect injection engine, after injecting fuel in the intake stroke toform a homogeneous air-fuel mixture in the cylinder, by injecting fuelin the compression stroke and forming a locally rich mixture near thespark plug, there is a case where combustion control is performed toachieve exhaust purification by PN suppression and improvement in fuelefficiency by performing weak stratified combustion.

In this case, as shown in FIG. 6, the injection timing (injectionperiod) between the cylinders may overlap in some cases. FIG. 6 shows,when it is defined as the first, second, third and fourth cylinders fromthe preceding cylinder, a case of a general in-line four-cylinder engineigniting in order of the first cylinder, the third cylinder, the fourthcylinder, and the second cylinder. In the period of 601, the injectionin the compression stroke in the third cylinder and the injection in theintake stroke in the fourth cylinder overlap. In the period of 602, theinjection in the intake stroke in the second cylinder and the injectionin the compression stroke in the fourth cylinder overlap. In the period603, the injection in the intake stroke in the first cylinder and theinjection in the compression stroke in the second cylinder overlap. Inthe period of 604, the injection in the compression stroke in the firstcylinder and the injection in the intake stroke in the third cylinderoverlap.

In the case where one boosting circuit 514 is arranged for eachcylinder, if the injection interval within the first cylinder issecured, when the fuel injection in the intake stroke and thecompression stroke overlaps among the cylinders, there is littlepossibility that the next re-injection is required in a state in which avoltage value of the high voltage source decreases. However, since thecharge accumulated in the capacitor 533 of the boosting circuit 514 isdischarged after a lapse of a certain period of time, when the drivingcycle of the boosting circuit 514 is delayed, the voltage value of thehigh voltage source may slightly decrease. Furthermore, in order toreduce heat generation and cost of the ECU 104, in a four-cylinderengine, there are cases where one boosting circuit 514 is provided foreach of the odd-numbered cylinders 1, 3 and the even-numbered cylinders2, 4, or one boosting circuit 514 is shared by the four cylinders. Byreducing the number of boosting circuits 514, the number of switchingelements including a transistor or the like securing withstand voltageand the number of capacitors capable of storing high voltage can bereduced, thereby reducing the cost of the drive circuit 103.

In addition, in the boosting circuit 514, in order to store the electriccharge in the capacitor 533, the switching element 531 is controlled torepeat ON/OFF at high frequency. In this case, the boosting circuit 514generates heat, so that the time of applying a high voltage to thesolenoid 202 or the current value that can be passed through thesolenoid 202 may be restricted. By reducing the number of the boostingcircuits 514, heat generation of the drive circuit 103 can besuppressed. Especially, even when the fuel pressure supplied to the fuelinjection device 540 becomes high, current control of the fuel injectiondevice 540 can be performed without being restricted by current. As aresult, it is possible to stably operate the fuel injection device 540with a high fuel pressure, and it is possible to improve the accuracy ofthe injection amount in the high fuel pressure range.

FIG. 7 shows, as an example, a condition (case) in which multistageinjection is performed with a configuration in which one boostingcircuit 514 is provided for each of the first and third odd-numberedcylinders and the second and fourth even-numbered cylinders. AlthoughFIG. 7 shows the first and third odd-number cylinders, the second andfourth even-numbered cylinders are also the same as in FIG. 7. In FIG.7, the drive current of the preceding cylinder (first cylinder) and thevalve body displacement amount in the case where the timing when theinjection pulse is turned ON is matched with the timing when theinjection pulse of the third cylinder is turned ON are indicated bybroken lines 712 and 713.

At a time before the timing t₇₁ at which the injection pulse of thethird cylinder is turned ON, the voltage value of the high voltagesource (boosting circuit) 514 is controlled to be the boosted voltageVH. At a timing t₇₁ at which the injection pulse of the third cylinderis turned ON, a voltage is applied to the solenoid 205 from the highvoltage source 514, and the electric charge stored in the capacitor 533decreases, so that the voltage value of the high voltage source 514decreases. At a timing t₇₂ at which the current reaches the peak currentI_(peak) the application of the voltage from the high voltage source 514to the solenoid 205 is stopped and the battery voltage source VB or 0 Vis applied to the solenoid 205. After a timing t₇₂, the voltage value ofthe high voltage source 514 returns toward the boosted voltage VH;however, before returning to the boosted voltage VH, the injection pulsein the compression stroke in the first cylinder is energized at timingt₇₃, and the voltage value of the high voltage source 514 decreases.Thereafter, when the timing reaches the timing t₇₄ at which the currentvalue of the first cylinder becomes the peak current I_(peak) thevoltage application from the high voltage source 514 to the solenoid 205is stopped; therefore, the current value returns to the boosted voltagevalue VH after a certain period of time has elapsed.

When the drive current 712 and the valve body displacement amount 713 ofthe first cylinder when the timing when the injection pulse is turned ONis matched with the timing when the injection pulse of the thirdcylinder is turned ON are compared with a drive current 710 of the thirdcylinder and a valve body displacement amount 711, since the voltagevalue applied to the solenoid 205 is lower in the first cylinder than inthe third cylinder, the current flowing in the solenoid 205 decreasesand the rise of the current is delayed. As a result, the rise of themagnetic attraction force generated in the mover 202 is also delayed.Therefore, the timing when the magnetic attraction force exceeds theforce in the valve closing direction acting on the valve body 214 andthe mover 202 is delayed, so that the valve opening start timing of thevalve body 214 is delayed from the timing t₇₅ to the timing t₇₆. Sincethe voltage value of the high voltage source does not affect the currentafter the current value flowing through the solenoid 205 reaches theholding current 721, the delay time from when the injection pulse isturned OFF to when the valve body 214 closes becomes equal between thefirst cylinder and the third cylinder.

Therefore, when comparing the injection amounts of the first cylinderand the third cylinder, a valve opening delay time of the first cylinderuntil the valve body 214 reaches the target opening degree after theinjection pulse is turned ON becomes longer, and the injection amountdecreases. When the voltage of the high voltage source 514 is lower thanthe boosted voltage VH at the timing when the injection pulse is turnedON, the injection pulse width is corrected so as to be longer than theinjection pulse width in the case where the voltage does not decrease,so that the injection amount is increased. This makes it possible tosuppress variation in the injection amount between the cylinders betweenthe first cylinder and the third cylinder.

This means that in the case of setting the pulse width of the injectionpulse to the energization time (for example, the injection pulse width815 in FIG. 8) that is closed after the drive current is switched to theholding current, the pulse width of the injection pulse in the casewhere the fuel injection timing or the fuel injection period overlapsbetween the cylinders is corrected so as to be longer than the pulsewidth of the injection pulse in the case where the injection timing orthe injection period does not overlap. Alternatively, this means that inthe case of setting the pulse width of the injection pulse to theenergization time (for example, the injection pulse width 815 in FIG. 8)at which the valve body is closed after the drive current is switched tothe holding current, the pulse width of the injection pulse in the casewhere the voltage of the high voltage source 514 decreases is correctedso as to be longer than the pulse width of the injection pulse in thecase where the voltage of the high voltage source does not decrease.

Since the amount of decrease in the injection amount depends on thevoltage value of the high voltage source 514, it is preferable todetermine the correction amount of the injection pulse according to thevoltage value of the high voltage source 514. Further, by connecting acontact 516 to the IC 502 or an A/D conversion port of the CPU 501,voltage detection means for detecting the voltage value of the highvoltage source, which is the output of the boosting circuit 514, may beprovided. In the present embodiment, the contact 516 is connected to theA/D conversion port of the IC 502 via the wiring 551. The relationshipbetween the injection amount, the voltage value of the high voltagesource 514, and the injection pulse width is preferably given to the CPU501 in advance. With such a configuration, it is possible to determinean appropriate injection pulse width Ti from the required injectionamount calculated by the CPU 501 and the detected voltage value of thehigh voltage source 514.

FIG. 7 shows a case where the pulse width Ti of the injection pulse issufficiently long. This corresponds to the case where the injectionpulse width Ti shown in FIG. 8 is longer than the pulse width at 814,and corresponds to a section indicated by the injection amountcharacteristic 830.

Next, the relationship (flow rate characteristic) between the injectionpulse width Ti and the injection amount will be described with referenceto FIG. 8.

First, a general flow rate characteristic will be described using theflow rate characteristic Q₈₀₁ in the case where the voltage of the highvoltage source 514 does not decrease. When the injection pulse width Tidoes not reach the fixed time and becomes smaller than 811, since themagnetic attraction force acting on the mover 202 does not exceed theforce in the valve closing direction acting on the valve body 214, thevalve body 214 does not start opening and fuel is not injected. Theforce in the valve closing direction is the resultant force of the forceof the spring 210 acting on the valve body 214 and the force due to thedifferential pressure of the fuel pressure acting on the valve body 214in the closed state described above.

Under a condition that the injection pulse width Ti is short, forexample, 801, the valve body 214 separates from the valve seat 218 andstarts to displace; however, since the valve closing starts before thevalve body 214 reaches the target opening degree, the injection amountdecreases with respect to a one-dot chain line 820 extrapolated from alinear region 830 in which the relationship between the injection pulsewidth and the injection amount becomes linear.

With the pulse width at the point 802, valve closing starts immediatelyafter reaching the target opening degree, and the locus of the valvebody 214 becomes parabolic motion. Under this condition, the kineticenergy of the valve body 214 in the valve opening direction is large andthe magnetic attraction force acting on the mover 202 is large, so thatthe proportion of the time required for closing the valve body 214increases, so that the injection amount increases with respect to theone-dot chain line 820.

With the injection pulse width at a point 803, the valve body 214 startsto close at the timing when the bound amount of the valve body 214caused by collision of the mover 202 with the fixed core 207 at thetiming when the valve body 214 reaches the target opening degree is themaximum. Therefore, a repulsive force when the mover 202 and the fixedcore 207 collide with each other acts on the mover 202, the valveclosing delay time from when the injection pulse is turned OFF untilwhen the valve body 214 closes becomes small. As a result, the injectionamount decreases with respect to the one-dot chain line 820.

At a point 804, since the injection pulse is stopped before the currentsupplied to the solenoid 205 reaches the holding current, the valveclosing delay time becomes longer, and the injection amount increaseswith respect to the one-dot chain line 820. Further, when the mover 202reaches the target opening degree and collides with the fixed core 207,and rebounds and then collides with the fixed core 207 again in thedirection of the fixed core 207, the valve opening delay time increasesdue to the kinetic energy of the mover 202. Therefore, even after thecurrent supplied to the solenoid 205 reaches the holding current, theinjection amount at the point 804 may become larger than the one-dotchain line 820 in some cases.

Furthermore, at the injection pulse width Ti which is larger than apoint 805 at which the bound of the valve body 214 converges and thecurrent reaches the holding current, the fuel injection amount linearlyincreases in accordance with the increase in the injection pulse widthTi.

In the region from the start of fuel injection to the pulse width Tiindicated by the point 804, even if the valve body 214 does not reachthe target opening degree or the valve body 214 reaches the targetopening degree, the bound of the valve body 214 is not stabilized, sothat the injection amount varies. In order to reduce the controllableminimum injection amount, it is necessary to increase the region inwhich the fuel injection amount increases linearly as the injectionpulse width Ti increases, or it is necessary to correct the injectionamount of the nonlinear region in which the relationship between theinjection pulse width Ti and the injection amount is not linear and theinjection pulse width Ti is shorter than the pulse width at 805.

In the flow rate characteristic Q₈₀₂ when the voltage of the highvoltage source 514 decreases, because the valve opening start timing ofthe valve body 214 is delayed for the reason explained in FIG. 7, thefuel injection timing is delayed from 811 to 812. In the case of theinjection pulse width 815, when the voltage decreases as compared withthe case where the voltage of the high voltage source 514 does notdecrease, the valve opening delay becomes longer, so that the injectionamount becomes smaller as indicated by 840. The relationship between thedrive current and the displacement amount of the valve body 214 underthis condition is as described in 710, 711, 712, and 713 in FIG. 7.

Also, in 804′ where the injection pulse width is smaller than the linearregion 830, there is a case where the injection amount becomes larger inthe case where the voltage is lower than when the voltage of the highvoltage source 514 does not decrease. At a point 804′, the displacementamount of the valve body 214 until the valve body 214 reaches the targetopening degree is equivalent to the point 805. In the case where thevalve closing delay time is the same between the condition where thevoltage of the high voltage source 514 does not decrease and thecondition where the voltage of the high voltage source 514 decreases,the injection amount becomes smaller in the case where the voltage ofthe high voltage source 514 is lower than when where the voltage doesnot decrease. However, when comparing the amount of displacement of thevalve body 214 after stopping the injection pulse, if the voltage of thehigh voltage source 514 decreases, the valve closing delay time becomeslonger and the area of the displacement amount of the valve body 214becomes larger. As a result, the injection amount is determined by thearea of the displacement amount of the valve body 214; therefore, in thecase where the voltage of the high voltage source 514 is lower than whenit is not decreased, the injection amount increases.

With reference to FIG. 9, the fuel injection amount at point 804′ willbe described. In FIG. 9, a drive current when the voltage value of thehigh voltage source 514 does not decrease is indicated by 910, adisplacement amount of the valve body is indicated by 911, a drivecurrent when the voltage of the high voltage source 514 decreases isindicated by 912, and a valve body displacement amount is indicated by913. In FIG. 7, the case where the pulse width Ti of the injection pulseis shorter than that in the case of FIG. 7 is shown. This corresponds tothe case where the injection pulse width Ti shown in FIG. 8 is the pulsewidth at 813. A waveform denoted by reference numeral 921 in FIG. 9 is aholding current supplied from the battery power source VB when theinjection pulse width Ti is assumed to be the same length as in FIG. 7.

As a first factor causing an increase in the injection amount, the timeit takes for the drive current to reach the peak current value I_(Peak)is delayed when the voltage of the high voltage source 514 is lower thanwhen the voltage of the high voltage source 514 does not decrease. As aresult of this delay, as shown in FIG. 9, the drive current value at atiming t₉₄ at which the injection pulse is turned OFF increases. As thedrive current value increases, the magnetic attraction force increasesand the valve closing delay time increases.

Even after the injection pulse is turned OFF, because of the influenceof the eddy current, a residual magnetic flux is generated in themagnetic member of the mover 202, the fixed core 207, and the housing203 constituting the magnetic circuit, and the magnetic attraction forceremains. The residual magnetic attraction force increases as the drivecurrent increases at the timing t₉₄ at which the injection pulse isturned OFF. As the residual magnetic attraction force increases, theforce acting on the mover 202 in the valve opening direction increases,and the valve closing delay time increases.

The second reason for the increase in the injection amount is the boundof the valve body 214 that occurs after the mover 202 reaches the targetopening degree. In the case where the voltage of the high voltage source514 does not decrease, after the bound of the valve body 214 caused bythe bound between the mover 202 and the fixed core 207 after the valvebody 214 reaches the target opening degree converges, the valve body 214starts to close from the target opening degree. On the other hand, inthe case where the voltage of the high voltage source 514 decreases, thebound that occurs after the valve body 214 reaches the target openingdegree does not converge and the valve closing operation is startedwhile the mover 202 is moving in the direction of the target openingdegree. Therefore, the valve closing delay time increases due to thekinetic energy of the mover 202.

The injection amount is determined by a tradeoff between the valveopening delay time and the valve closing delay time. In the case wherethe voltage is lower than when the voltage of the high voltage source514 does not decrease, the injection amount until the injection pulse isturned OFF becomes small and the injection amount from the turning offof the injection pulse to the completion of closing of the valve body214 becomes large. As a result, with the injection pulse width 815, ascompared with the injection pulse width 815 of a linear region (linearregion) 830, there is a case that the injection amount becomes larger inthe case where the deviation of the injection amount changes in apositive direction or the voltage is lower than when the voltage of thehigh voltage source 514 does not decrease.

In the linear region 830, in the case where the voltage of the highvoltage source 514 is lower than when the voltage of the high voltagesource 514 does not decrease, it is preferable to correct so that theinjection pulse width becomes long. Thus, it is possible to suppress thechange in the injection amount caused by the valve opening delay. Such acorrection of the injection pulse width is preferably performed by thedrive device 150. On the other hand, in the case of setting the pulsewidth of the injection pulse to the energization time (the injectionpulse width 804 in FIG. 8) at which the valve body is closed before thedrive current is switched to the holding current, the pulse width of theinjection pulse in the case where the voltage of the high voltage source514 decreases may be corrected so as to be shorter than the pulse widthof the injection pulse in the case where the voltage of the high voltagesource does not decrease.

Further, the amount of change in the injection amount due to thedecrease in the voltage of the high voltage source 514 depends on thevoltage value of the high voltage source 514. Therefore, the contact 516is connected to the IC 502 or the A/D conversion port of the CPU 501 sothat the voltage value of the high voltage source 514 which is theoutput of the boosting circuit 514 can be detected, the relationshipbetween the injection amount, the voltage value of the high voltagesource 514, and the injection pulse width is preferably given to the CPU501 in advance. With such a configuration, it is possible to determinean appropriate injection pulse width Ti from the required injectionamount calculated by the CPU 501 and the detected voltage value of thehigh voltage source 514.

Under a condition of multistage injection, in order to inject theinjection amount realized by one injection so far divided into aplurality of injections, it is necessary to reduce the minimum injectionamount controllable by one injection. In this case, since the injectionamount is limited in the linear region 830, it is necessary toaccurately control the injection amount in the region where theinjection pulse width Ti is smaller than the point 805.

The injection amount for the injection pulse width Ti from 813 to 814under a condition that the voltage value of the high voltage source 514decreases also depends on the current value at the timing at which theinjection pulse is turned OFF. Both ends of the resistor 508 or theresistor 513 are connected to the A/D conversion port of the CPU 501 orthe IC 502, and current detection means for detecting the current valueafter the drive current reaches the peak current I_(peak) may beprovided. With this configuration, a current is detected immediatelybefore the timing when the injection pulse is stopped, and the currentvalue at timing when the injection pulse is turned OFF can be estimatedfrom the current value.

In the case where the correction of the injection amount with respect tothe injection under a condition that the current value is detected afterthe detection of the current value cannot be made in time, the injectionpulse width in the next injection may be corrected so that the injectionamount for the amount of change in the injection amount in the previousinjection under a condition of the next multistage injection in onecombustion cycle is corrected. With such a correction, the total amountof the injection amount during one combustion cycle in the case ofperforming the multistage injection can be matched between cylinders andfor each cycle. Therefore, it is possible to suppress an increase in PNcaused by the deviation of the injection amount from the required value.

The relationship between the injection amount, the voltage value of thehigh voltage source 514, the drive current value, and the injectionpulse width Ti may be previously given to the CPU 501 or the IC 502 asMAP information or approximate expression. With such a configuration,the correction amount of the injection pulse is calculated from theestimated current value, and the injection pulse width necessary forachieving the required injection amount can be appropriately determined.As a result, it is possible to suppress variations in the injectionamount in a range where the injection pulse width is smaller than theinjection pulse width 814 caused by the decrease in the voltage value ofthe high voltage source 514, thereby accurately controlling theinjection amount even under a condition of multistage injection.

The current value at the timing when the injection pulse is turned OFFis influenced by the voltage value of the high voltage source 514 andthe resistance value of the solenoid 205. The resistance value of thesolenoid 205 increases as the solenoid 205 generates heat. However,under a condition that the injection timing or the injection periodbetween the cylinders overlap due to the multistage injection and thevoltage of the high voltage source 514 decreases, the drive cycle of thefuel injection device 540 contributing to the heat generation of thesolenoid 205, and the like are equal. Therefore, if the voltage value ofthe high voltage source 514 can be detected, the current value at thetiming when the injection pulse is turned OFF can be estimated.Therefore, the voltage value of the high voltage source 514 may bedetected immediately before the fuel injection timing, and thecorrection amount of the injection pulse width may be determined fromthe detected value.

When the voltage value of the high voltage source 514 is detected by theCPU 501 and the IC 502, the time resolution of the A/D conversion portis restricted due to limitations of hardware. In this case, it ispreferable to detect the voltage value of the high voltage source 514with the energization timing of the injection pulse calculated by theCPU 501 as a trigger. With such a configuration, it is possible todetect the voltage value of the high voltage source 514 necessary forcorrecting the injection pulse width at an appropriate timing withoutincreasing the use frequency and the resolution of the A/D conversionport, thereby improving the correction accuracy of the injection amount.

In FIG. 8, the injection amount deviation is indicated by the ratio ofthe injection amount Q₈₀₂ in the case where the voltage with respect tothe injection amount Q₈₀₁ in the case where the voltage of the highvoltage source 514 does not decrease decreases. Therefore, an injectionamount deviation 860 is larger than the injection amount deviation 840.However, in the region where the injection amount deviation 840 occurs,since the injection amount Q₈₀₁ is larger than the injection amountQ₈₀₂, the absolute value of the correction amount of the injection pulsewidth necessary for correcting the injection amount deviation 860becomes smaller than the absolute value of the correction amount of theinjection pulse width necessary for correcting the injection amountdeviation 840. Therefore, the absolute value of the correction amount ofthe injection pulse width necessary for correcting the injection amountdeviation 860 in the injection pulse width 813 and further correctingthe injection amount so as to match the one-dot chain line 820extrapolated from the linear region 830 is smaller than the absolutevalue of the correction amount of the injection pulse width necessaryfor correcting the injection amount deviation 840 (the correction amountof the injection pulse width necessary for matching the injection amountQ₈₀₁).

Therefore, in a region where the injection pulse width is smaller thanthe injection pulse width 814 as compared with the region in which theinjection pulse width is larger than the injection pulse width 814, itis preferable to correct so that the absolute value of the correctionamount of the injection pulse width in the case where the voltage of thehigh voltage source 514 decreases becomes small. By switching thecorrection amount of the injection pulse width in this way, it ispossible to suppress variation in the injection amount caused by thefact that voltage of the high voltage source 514 decreases in the rangefrom the linear region 830 to the region where the injection pulse widthis small.

This means that in the case of setting the pulse width of the injectionpulse to the energization time (for example, the injection pulse width813 in FIG. 8) at which the valve body is closed before the drivecurrent is switched to the holding current, the absolute value of thecorrection amount of the pulse width of the injection pulse is lowerthan when the pulse width of the injection pulse is set to theenergization time at which the valve body is closed after the drivecurrent is switched to the holding current (for example, the injectionpulse width 815 in FIG. 8)

Also, from 604, under a condition that the injection interval of thecompression stroke injection of the first cylinder is small or theinjection interval of the intake stroke injection of the third cylinderis small, even when the injection timing and the injection period do notoverlap in the first cylinder and the third cylinder, fuel injection maybe performed under a condition that the voltage of the high voltagesource 514 decreases. In this case, even if the boosting circuit 514 isconfigured for each cylinder, fuel injection is performed under acondition that the voltage of the high voltage source 514 decreases;therefore, variation in the injection amount occurs in the firstinjection and the second injection during the corresponding stroke. Evenin such a case, it is possible to suppress variation in the injectionamount by correcting the injection pulse width described in FIGS. 6, 7,8, and 9.

Next, with reference to FIGS. 10 and 11, a description will be given ofa variation correction method of the injection timing when the voltagevalue of the high voltage source 514 decreases. In the valve bodydisplacement amount shown in FIG. 10, the valve body displacement amountin the case where the voltage value of the high voltage source 514 atthe timing when the injection pulse is turned ON becomes a boostedvoltage VH that is an initial value and under a condition that the fuelpressure is small is indicated by 1001, and the valve body displacementamount under a condition that the fuel pressure is high is indicated by1003. Furthermore, in FIG. 10, the valve body displacement amount in thecase where the voltage value of the high voltage source 514 at thetiming when the injection pulse is turned ON is lower than the initialvalue and under a condition that the fuel pressure is small is shown at1002, and the valve body displacement amount under a condition that thefuel pressure is high is shown at 1004. For the three conditions withdifferent fuel pressures shown in FIG. 11, it is assumed that fuelpressures are 1101, 1102, and 1103 in descending order.

As described in FIG. 7, when the voltage value of the high voltagesource 514 decreases from the initial value and the voltage applied tothe solenoid 205 decreases, the valve opening start timing of the valvebody 214 is delayed, and the fuel injection timing is delayed. Forexample, when the injection timing of fuel is delayed under thecondition of fuel injection in the compression stroke, the fuel sprayeasily adheres to the piston, and the formation state of the fuel sprayis changed, so that the homogeneity of the spray decreases. Attachmentof the fuel spray to the piston and decrease in homogeneity of the spraycan lead to an increase in PN.

Further, even in the condition of fuel injection in the intake stroke,the fuel injection timing is delayed, so that the timing of fuelinjection is delayed with respect to the opening/closing timing of theintake valve. The homogeneity of the air-fuel mixture of the air flowinginto the piston cylinder and the injected fuel varies for each cylinderor for each injection of multistage injection, so that the PN mayincrease.

In order to suppress variation in the fuel injection timing due to adecrease in the voltage value of the high voltage source 514,preferably, the voltage value of the high voltage source 514 or thecurrent flowing through the solenoid 205 is detected by the CPU 502 orthe IC 501, and the amount of decrease from the voltage value of thehigh voltage source 514 or the boosted voltage VH is calculated from thedetected value to correct the energization timing of the injectionpulse.

As indicated by 1102 in FIG. 11, the relationship between the voltagevalue of the high voltage source 514 and the fuel injection timing issubstantially linear. The relationship between the voltage value of thehigh voltage source 514 and the injection timing is preferably given tothe CPU 501 in advance. With such a configuration, by determining theappropriate injection timing from the detected voltage of the highvoltage source 514 and making the energization timing (applicationtiming) of the energizing pulse faster by the amount of deviation fromthe reference value, it is possible to accurately correct variations inthe injection timing.

In addition, the valve body 214 starts valve opening at the timing whenthe magnetic attraction force acting on the mover 102 exceeds the forcein the valve closing direction acting on the valve body 214 and themover 102. The magnetic attraction force acting on the mover 102 isdetermined by the current value I_(so) flowing in the solenoid 205.Assuming that the voltage value of the high voltage source 514 is V_(Hi)and the resistance value of the solenoid 205 is R_(SO), the currentvalue I_(so) is obtained by I_(so)=V_(Hi)/R_(SO) according to Ohm's law.Since the resistance value R_(SO) of the solenoid 205 varies with theheat generation of the solenoid 205, by detecting the current Iso, thecalculation accuracy of the correction value of the energization timingcan be improved, as compared with the case where the energization timingis corrected only with the voltage value V_(Hi) of the high voltagesource. As a result, the correction accuracy of the valve opening starttiming of the valve body 214 can be enhanced, and the effect ofsuppressing PN is enhanced.

In the correction of energization timing by the current value, it ispreferable to detect the current value before the valve body 214 startsto open after the start of energization to the solenoid 205, and todetermine the correction amount of energization timing according to thedetected current value. In the detection of the current value, it ispreferable to use the energization timing as a trigger. With such aconfiguration, since it is possible to reliably detect the current valueafter energization of the solenoid 205 is started, the calculationprecision of the correction amount of energization timing is improvedand the correction accuracy of the valve opening start timing can beenhanced.

Furthermore, the current value Iso during the period from the start ofthe energization to the solenoid 205 until the valve body 214 opens isdetected at two or more points, and the correction amount ofenergization timing may be determined using the inclination of thecurrent value Iso, that is, time differentiation or an approximateexpression. With such a configuration, the influence of the detectionerror of the current Iso can be reduced as compared with the case ofdetecting one point of the current value Iso, so that it is possible toimprove the correction accuracy of the valve opening start timing.

The relationship between the voltage value and the drive current of thehigh voltage source 514 and the correction amount of the energizationtiming of the injection pulse may be previously given to the CPU 501 asMAP data or an approximate expression. The energization timing can beappropriately determined from the current value detected by such aconfiguration and the voltage value of the high voltage source 514, andvariation in the injection timing can be suppressed.

Furthermore, the delay in the energization timing of the injection pulsewhen the voltage value of the high voltage source 514 decreases isinfluenced by the fuel pressure supplied to the fuel injection device540. Under the condition of 1101 having a high fuel pressure withrespect to 1102 or 1103 having a small fuel pressure, the sensitivity ofthe change in the fuel injection timing due to the decrease in thevoltage value of the high voltage source 514 is different. The higherthe fuel pressure, the larger the inclination of the fuel injectiontiming with respect to the voltage value of the high voltage source 514.In the closed state of the valve body 214, the force in the valveclosing direction acting on the valve body 214 when the fuel pressure issmall is indicated by 1007, and the force in the valve closing directionacting on the valve body 214 when the fuel pressure is high is indicatedby 1006.

In a state where the valve body 214 is closed, the resultant force ofthe fluid force obtained by multiplying the cross sectional area of thediameter of the valve body 214 and the valve seat 218 by the fuelpressure and the spring load 210 acts as the force in the valve closingdirection. When the injection pulse is turned ON, a drive current issupplied to the solenoid 205, and a magnetic attraction force acts onthe mover 202 with a time delay due to the influence of the eddycurrent. Under a condition that the voltage value of the high voltagesource 514 does not decrease under the condition of 1007 where the fuelpressure is low, as indicated by 1001, the valve body 214 starts to openafter the timing t₁₀₂ at which the magnetic attraction force exceeds theforce 1007 in the valve closing direction. Under a condition that thevoltage value of the high voltage source 514 decreases, the valve body214 starts to open after the timing t₁₀₃ as indicated by 1002.

Here, a difference in the valve opening start timing between the casewhere the voltage of the high voltage source 514 does not decrease andthe case where the voltage of the high voltage source 514 decreasesunder the condition of 1007 where the fuel pressure is low is set to1010. Also, a difference in the valve opening start timing between thecase where the voltage of the high voltage source 514 does not decreaseand the case where the voltage of the high voltage source 514 decreasesunder the condition of 1006 where the fuel pressure is high is set to1011. As shown in FIG. 10, the valve opening start timing difference1011 is larger than the valve opening start timing difference 1010.

The magnetic attraction force acting on the mover 202 depends on theenergy of the drive current, that is, the time integral value of thedrive current. As the voltage value of the high voltage source 514decreases, the inclination of the drive current decreases and theinclination of the magnetic attraction force also decreases. Compared tothe condition of 1007 in which the fuel pressure is small due to thedifference in inclination, the delay of the valve opening start timingand the injection timing in the case where the voltage of the highvoltage source 514 decreases is larger in 1006 where the fuel pressureis higher. Therefore, by detecting the fuel pressure supplied to thefuel injection device 540 detected, and determining the energizationtiming for correcting the injection timing according to the fuelpressure and the voltage value of the high voltage source 514, it ispossible to suppress variations in the injection timing.

Furthermore, by connecting the signal from the pressure sensor 102 tothe A/D conversion port of the CPU 501, it is preferable to providepressure signal detection means for detecting the fuel pressure. Thedetection of the fuel pressure may be carried out by detecting the fuelpressure at timing before the trigger, with the energization timing ofthe injection pulse calculated by the CPU 501 as a trigger. When thepressure drops due to the fuel injection, the pressure in a rail piping133 fluctuates, and the pressure detected by disconnecting the pressuresensor 102 also varies. By detecting the fuel pressure before the fuelinjection, it is possible to accurately detect the fuel pressureimmediately before the valve opening timing of the valve body 214 whichcontributes to the change in the injection timing, thereby accuratelycalculating the correction amount of the energization timing. As aresult, variation in injection timing can be suppressed, and the effectof suppressing PN is enhanced.

Example 2

With reference to FIGS. 8 and 12, a method of correcting the injectionamount variation in the second embodiment of the present invention willbe described. The fuel injection device and the drive device in thepresent embodiment have the same configuration as in the firstembodiment. FIG. 12 is a view showing, in a case where a voltage valueof a high voltage source does not decrease and a case where the voltagevalue decreases, a drive current and a valve body displacement amount atan injection pulse width at a point 815 in FIG. 8, and a drive currentand a valve body displacement amount at an injection pulse width at apoint 802, for a drive device for a fuel injection device according to asecond embodiment.

In FIG. 12, at the injection pulse width at the point 802 in FIG. 8, adrive current waveform in the case where the voltage of the high voltagesource 514 does not decrease compared with the initial value (boostedvoltage VH) is indicated by 1201, a valve body displacement amount isindicated by 1202, and a current waveform when the voltage of the highvoltage source 514 decreases compared with the initial value isindicated by 1203, and a valve body displacement amount is indicated by1204. Furthermore, at the injection pulse width at the point 815, acurrent waveform in the case where the voltage of the high voltagesource 514 does not decrease compared with the initial value isindicated by 1205, a displacement amount of the valve body is indicatedby 1206, and a current waveform when the voltage of the high voltagesource 514 decreases compared with the initial value is indicated by1207, and a valve body displacement amount is indicated by 1208.

First, a method of correcting the injection amount in the region wherethe injection pulse width is smaller than the point 802 will bedescribed. With the injection pulse width at the point 802, valveclosing starts immediately before reaching the target opening degree,and the locus of the valve body 214 becomes parabolic motion. In otherwords, within the range of the pulse width of the point 802 or less, thevalve body 214 is driven under the condition of the half lift in whichthe valve body 214 is closed without reaching the target opening degree.Under this condition, the valve body displacement amount increases alongwith the valve closing delay time according to the injection pulse ascompared with a condition that the energization is stopped after thevalve body 214 reaches the target opening degree; therefore, thesensitivity of the injection pulse width to the injection amount ishigh. As a result, in comparison with the condition that the valve body214 reaches the target opening degree and starts closing, under thecondition of half lift, when the voltage of the high voltage source 514decreases from the initial value boosted voltage VH, it is preferable tocorrect the correction amount of the injection pulse width to a largeextent as compared with the case where the voltage does not decrease.

Also, under the condition of half lift, in the case where the voltage ofthe high voltage source 514 decreases from the initial boosted voltageVH, the drive current value at the timing of stopping energization islower than when the voltage does not decrease. Furthermore, when thevoltage of the high voltage source 514 decreases from the initialboosted voltage VH, the kinetic energy of the valve body 214 and themover 202 is small at the timing of stopping energization as the valveopening start timing is delayed, as compared with the case where thevalve body 214 and the mover 202 do not decrease. From these facts, themaximum value 1210 of the displacement amount of the valve body 214becomes small. Therefore, under a condition that the valve body 214 isdriven by the half lift, when the voltage of the high voltage source 514decreases from the initial boosted voltage VH, by correcting so that theinjection pulse width becomes larger than when not decreasing, variationin the injection amount can be suppressed, so that it is possible toimprove the correction accuracy of the injection amount.

It should be noted that the present invention is not limited to theembodiments described above, but includes various modified examples. Forexample, the above-described embodiments have been described in detailin order to explain the present invention in an easy-to-understandmanner, and are not necessarily limited to those having all theconfigurations. In addition, it is possible to replace part of theconfiguration of one embodiment with the configuration of anotherembodiment, and the configuration of another embodiment can be added tothe configuration of one embodiment. Furthermore, it is possible to add,delete and replace other configurations with respect to part of theconfiguration of each embodiment.

REFERENCE SIGNS LIST

-   101A, 101B, 101C, 101D Fuel injection device-   102 Pressure sensor-   103 Drive circuit-   104 Engine control unit (ECU)-   150 Drive device-   202 Mover-   205 Solenoid-   207 Fixed core-   210 Spring-   212 Return spring-   214 Valve body-   218 Valve seat-   219 Fuel injection hole-   401 High voltage-   402 Current-   403 Holding current-   404 Predetermined current value-   501 CPU-   502 Driving IC-   503 Communication line-   505, 506, 507 Switching element-   508 Resistance-   509, 510, 511 Diode-   512, 513 Resistance-   514 Boosting circuit (high voltage source)-   515 Contact potential-   530 Coil-   531 Transistor-   532 Diode-   533 Capacitor-   535 Diode-   540 Fuel injection device-   550, 551, 580, 581, 552, 553 Wiring-   590 Power source side terminal of solenoid 205-   710 Drive current of third cylinder-   711 Valve body displacement amount of third cylinder-   712 Drive current of first cylinder-   713 Valve body displacement amount of first cylinder-   830 Linear area (linear area)-   910 Drive current when voltage value of high voltage source-   514 does not decrease-   911 Valve body displacement amount when voltage value of high    voltage source 514 does not decrease-   912 Drive current when voltage of high voltage source 514 decreases-   913 Valve body displacement amount when voltage of high voltage    source 514 decreases-   1001 Valve body displacement amount when voltage value of high    voltage source 514 is boosted voltage VH and under condition that    fuel pressure is small-   1002 Valve body displacement amount when voltage value of high    voltage source 514 decreases from initial value and under condition    that fuel pressure is small-   1003 Valve body displacement amount when voltage value of high    voltage source 514 is boosted voltage VH and under condition that    fuel pressure is high-   1004 Valve body displacement amount when voltage value of high    voltage source 514 decreases from initial value and under condition    that fuel pressure is high-   1010, 1011 Difference in valve opening start timing-   1101, 1102, 1103 Relationship between voltage value of high voltage    source 514 and fuel injection timing under three conditions of    different fuel pressures

The invention claimed is:
 1. A drive device for an electromagnetic fuelinjection device to inject fuel by driving a valve body employing amagnetic attraction force generated by energizing a solenoid, the drivedevice comprising a function of: controlling a time for energizationsupplied to the solenoid from a voltage source with a pulse width of aninjection pulse; correcting the pulse width of the injection pulse whena voltage of the voltage source is a second voltage lower than a firstvoltage to be longer than the pulse width of the injection pulse whenthe voltage of the voltage source is the first voltage; and making acorrection amount of the pulse width of the injection pulse, when thevalve body is controlled such that it starts to close before reaching atarget opening degree since beginning to open, larger than thecorrection amount of the pulse width of the injection pulse when thevalve body is controlled such that it starts to close after reaching thetarget opening degree.
 2. A drive device for an electromagnetic fuelinjection device to inject fuel by driving a valve body employing amagnetic attraction force generated by energizing a solenoid, the drivedevice comprising a function of: controlling a time for energizationsupplied to the solenoid from a voltage source with a pulse width of aninjection pulse; correcting the pulse width of the injection pulse whena voltage of the voltage source is a second voltage lower than a firstvoltage to be longer than the pulse width of the injection pulse whenthe voltage of the voltage source is the first voltage; and making acorrection amount of the pulse width of the injection pulse, when a peakcurrent to open the valve body is cut off during a peak current supplyperiod in which the peak current is supplied to the solenoid based on adrive voltage applied from the voltage source, larger than thecorrection amount of the pulse width of the injection pulse when aholding current smaller in current value than the peak current is cutoff during a holding current supply period in which the holding currentis supplied to the solenoid.
 3. A drive device for an electromagneticfuel injection device to inject fuel by driving a valve body employing amagnetic attraction force generated by energizing a solenoid, the drivedevice being configured to control a drive voltage applied from avoltage source to the solenoid to supply a drive current to thesolenoid, the drive device comprising a function of: correcting one ofthe drive voltage and the drive current to increase an injection amountof the fuel when a voltage of the voltage source is a second voltagelower than a first voltage in comparison with a case where the voltageof the voltage source is the first voltage; and correcting one of thedrive voltage and the drive current to make an increased injectionamount of the fuel according to the correction under a half liftcondition in which the valve body closes before reaching a targetopening degree larger than the increased injection amount of the fuelaccording to the correction under a full lift condition in which thevalve body closes after reaching the target opening degree.
 4. The drivedevice for an electromagnetic fuel injection device according to claim1, the drive device comprising a function of correcting an energizationstart timing to the solenoid when the voltage of the voltage source isthe second voltage to be earlier than the energization start timing tothe solenoid when the voltage of the voltage source is the firstvoltage.
 5. The drive device for an electromagnetic fuel injectiondevice according to claim 2, the drive device comprising a function ofcorrecting an energization start timing to the solenoid when the voltageof the voltage source is the second voltage to be earlier than theenergization start timing to the solenoid when the voltage of thevoltage source is the first voltage.
 6. The drive device for anelectromagnetic fuel injection device according to claim 3, the drivedevice comprising a function of correcting an energization start timingto the solenoid when the voltage of the voltage source is the secondvoltage to be earlier than the energization start timing to the solenoidwhen the voltage of the voltage source is the first voltage.
 7. Thedrive device for an electromagnetic fuel injection device according toclaim 1, the drive device comprising a function of correcting anenergization start timing to the solenoid when a pressure of an injectedfuel is a first pressure to be earlier than the energization starttiming to the solenoid when the pressure of the injected fuel is asecond pressure smaller than the first pressure.
 8. The drive device foran electromagnetic fuel injection device according to claim 2, the drivedevice comprising a function of correcting an energization start timingto the solenoid when a pressure of an injected fuel is a first pressureto be earlier than the energization start timing to the solenoid whenthe pressure of the injected fuel is a second pressure smaller than thefirst pressure.
 9. The drive device for an electromagnetic fuelinjection device according to claim 3, the drive device comprising afunction of correcting an energization start timing to the solenoid whena pressure of an injected fuel is a first pressure to be earlier thanthe energization start timing to the solenoid when the pressure of theinjected fuel is a second pressure smaller than the first pressure. 10.The drive device for an electromagnetic fuel injection device accordingto claim 1, wherein the voltage source is provided with a boostingcircuit to boost a battery voltage.
 11. The drive device for anelectromagnetic fuel injection device according to claim 2, wherein thevoltage source is provided with a boosting circuit to boost a batteryvoltage.
 12. The drive device for an electromagnetic fuel injectiondevice according to claim 3, wherein the voltage source is provided witha boosting circuit to boost a battery voltage.
 13. The drive device foran electromagnetic fuel injection device according to claim 1, whereinthe drive device controls drive of the fuel injection device provided ineach of a plurality of cylinders.
 14. The drive device for anelectromagnetic fuel injection device according to claim 2, wherein thedrive device controls drive of the fuel injection device provided ineach of a plurality of cylinders.
 15. The drive device for anelectromagnetic fuel injection device according to claim 3, wherein thedrive device controls drive of the fuel injection device provided ineach of a plurality of cylinders.
 16. The drive device for anelectromagnetic fuel injection device according to claim 1, wherein afuel injection during one combustion stroke is performed while beingdivided into a plurality of times.
 17. The drive device for anelectromagnetic fuel injection device according to claim 2, wherein afuel injection during one combustion stroke is performed while beingdivided into a plurality of times.
 18. The drive device for anelectromagnetic fuel injection device according to claim 3, wherein afuel injection during one combustion stroke is performed while beingdivided into a plurality of times.